# My star will explode as a supernova. What can I do in order to ensure that my planet survives that?

I am posting this in behalf of a friend of mine from a distant world. Here is his message properly translated to English:

Hi, Sol3αlings1. My name is $ѬӚᕕƨ⧬௵44ħ$. We are peacefully and we need your help. I am a scientist/engineer from the planet $⋒◥27⟑▓⍫⋒இǪ$. We calculated that our home star, already an instable red giant, will explode as a supernova in some years.

Our home planet is small, but we have very highly advanced technology at our hands. Our planet is orbiting our home star at an orbit that in its median is a mildly temperate orbit, not too close to be scorching nor too distant to freeze out the planet. Our star is very unstable, as all red giants are, and it may enlarge and shrink chaotically, which would occasionally toast or freeze our planet, but our technology is able to easily cope with that. Exactly, our planet is in a $38.6\text{ }⛮֍㐃$-wide orbit2.

Our problem is that we want that our home planet be able to survive the supernova explosion, but we can't figure out how, so we're sending this signal seeking for your help. We don't want to take refuge elsewhere or just flee, we just want to find a way that allows our planet's surface and atmosphere to survive as much as possible. Having a lump of devastated planetary core and vaporized mantle behind and declaring it as "survived" is not of any use to us.

Further, I am aware of your communication "If the sun were to go supernova, how long would Earth have before it was consumed?" that makes clear that if we don't intervene, nothing of our planet will be left behind. Also, we know about "Can a planet survive a supernova?", but it is not very useful to us, because that was directly to planets which could naturally survive the explosion while we will use our most advanced technologies instead. Also, we know from "If the sun were to go supernova, how long would Earth have before it was consumed?" that if we don't intervene, nothing of our planet will be left behind.

We are also aware of "How can we extinguish a supernova?", but we don't want to either prevent or stop the supernova, but for some... huh... well... RELIGION (yes that is it) reasons that huh... well... our deity asked to us (haha), we now understand that the star needs to reach its natural destiny, but our planet should remain as our lively peace of rock, even if it ends being a very cold one.

So, how could we make our planet survive afterall?

You may think that it is strange that we ask you for that instead of finding the answer ourselves, since we are a very advanced technological civilization. But there is a very simple answer for that. It is easily explainable due to $⍬ईШ3877]֍$

error - signal lost
error - data truncated
error - data consistency check failed
error - syntatic token limit out of bounds
fatal - unexpected failure 15894
and file a bug report after checking for duplicates.
Don't forget to inform your transceiver configuration parameters.
info - signal recovered, data reception will be resumed


$Ш568ԖѼ⋒45993⋒ᐉ$ be thick enough, or maybe not completelly, otherwise it won't work. Very simple, isn't it?

I greatly appreciate your help. We are very sure of your peacefully collaboration.

Also, I got this other transmission from my space friend talking to one of his other friends. Looks like some sort of random gossip:

Are you an idiot? I order you to stop right now if you don't want to be executed for insubordination and stupidity. We need to keep our datacenter nearby that freaking3 star when it explodes to collect as much energy possible in order to decrypt the data, not to take it far away.

The only thing that we are still lacking is to find a way to not vaporize our orbiting datacenter-planet before we proccess all the data, and I already told you stop insisting in that moronic idea of "just running away". We're not robotizing an entire planet to just send it to somewhere else, running away like a bunch of $ѦܮḺஹआ$4! That wouldn't make any sense! That won't decrypt the message! So, please, please, keep the focus in your task which as I already told you like $2,985,984$ times is just to preserve the datacenter intact during the explosion until we decrypt that freaking3 message.

Now go back to your actual work, because it is only your department that is behind the schedule, otherwise you will know what is feeling real pain. Even the guys from the stellar Dyson-sphere could figure out how to collect and store the explosion energy, but you on the other hand, seems to be a complete incompetent!

End of secret transmission. Disclosing or leaking the content of this transmission is a crime punishable with a cruel death.

So, that is it: How could we make a planet survive a supernova explosion without it being vaporized or even significantly eroded? There is a very advanced alien civilization working and spending resources on that.

1: A Sol3αling is an inhabitant of some planet called "Sol-3α", i.e. the α-body in the third orbit around some star called "Sol". Could you guess which planet is that?

2: Sorry, I lost my table for converting that distance to Earth-like measurement units, so I don't know exactly how much is $38.6\text{ }⛮֍㐃$. Maybe you could provide the numbers that seems to work best while I search for the table and do the conversion so we don't lose any time?

3: Unsure of the translation of this term. Maybe there is another suitable word starting with the letter "f"?

4: This is some sort of animal-like creature that fears everything and instinctively run away from anything that remotely could pose any danger. A somewhat near translation to English in the sense it was used in the context would be to "running away like a bunch of coward chickens".

BTW, I found out that $2,985,984 = 12^6$. Maybe they count using base 12?

• The aliens may engineer/build anything that they want that do not violate the laws of physics.

• In fact they do not need to preserve living beings in the planet. It is just a robotized planet. I.e, a piece of rock that was converted to a giant planet-sized datacenter. Whatever is its atmosphere or surface composition, it is very different than something that would be created by nature. However, whatever is the data-processing hardware that they use in the planet, it must survive the explosion.

• Running away, i.e. just moving the planet to somewhere very far from the supernova, do not solves the problem. The aliens need to keep the planet around the supernova. In fact, they are interested in this planet exactly because the star will explode as a supernova.

Note for everybody: I had a lot of answers (21 non-deleted so far), so it was a hard time to nail down the very best.

No answer was perfect. All of them either misses something, contains flaws, are incomplete, overly simplify something, break or abuse the rules, presume some sort of doubtful at best speculative physics, contains some sort of gap or something left vague and unexplained, etc. None of them would give a definitive solid answer if this question had the tag . Intuition says that it is impossible in , but being able to prove that there is simply no way ever to manipulate space-time, dark-matter, or whatever else for that (or prove instead that this is indeed possible somehow) is probably way beyond our present-day knowledge level in physics. However, since this question do not have that tag, this is ok.

Anyway, the answers which I consider somewhat acceptable are from Thucydides, John Dallman, Jim2B, Bob Gray, Physicist137, a4android's longer answer and my own non-wiki answer. All of the non-deleted answers posted so far provide some sort of valuable information and insight, even those that are flawed, incomplete or missing the point in some way. Further, almost all of the comments in the question and in most of the answers were very helpful also.

Finally, after a lot of thinking and reasoning with myself, I considered Bob Gray's answer the best (by a tiny margin over the others), so I accepted his answer. Probably, many people will disagree and I am also very unsure myself because I had too many good and very different answers without any of them being perfect or clearly the best.

Finally, I will still evaluate eventual further answers.

• Comments are not for extended discussion; this conversation has been moved to chat. Please continue the fun there! – Monica Cellio Jul 19 '16 at 15:57
• Many thanks for not only choosing your preferred answer but for explaining why you choose it. Also, for saying you were unsure about your choice. I'm not knocking Bob Gray's answer, because if the choice had been mine I would have chosen it too (assuming I couldn't vote for my own). It would be wonderful on WB if more OP's explained their reasoning for their choices too. I salute you for setting a high standard. – a4android Jul 21 '16 at 5:13
• One interesting complication. So, you protect the planet from the supernova. Then what? There is no star for your planet to orbit around. If there is, it is a black hole. Or a neutron star. Or, well, something else. But it is not a star. Certainly nothing with the same gravity. What do you do AFTER you save the planet? Seems there is no longer any reason to keep the planet where it is. In fact, I doubt if the planet WILL stay where it is. The law of Unintended Consequences of Pointy-Haired Bosses. They have a history of solving the wrong problem.. How do you survive AFTER you survive? – Justin Thyme Sep 29 '18 at 3:15

All you'd need is an Einstein-Rosen bridge situated so that it was placed perpendicular to the planet. Make the entrance, say, 2 planetary diameters wide and just let it sit there.

The energy from the supernova that would have impacted the planet will instead go into the wormhole and come out wherever. I say place the other end near another supernova and hit one supernova with the other. Interesting!

The huge width of the bridge would stop any "bleed-around" energy from leaking through and hitting your planet. Sit back and watch the show!

• Good solution! Very simple and creative. :D – Victor Stafusa Jul 17 '16 at 2:22
• Don't forget about the supernova afterglow - all that highly radioactive material created in the supernova is everywhere around you, producing quite lethal amounts of gamma radiation (among other fun things). – Luaan Jul 18 '16 at 8:22
• "I say place the other end near another supernova and hit one supernova with the other. Interesting!" lmao, when life hands you lemons... – underscore_d Jul 19 '16 at 14:52
• How to create a large and stable bridge? – Dávid Horváth Jul 20 '16 at 18:34
• @DávidHorváth Pretty sure if anyone could answer that they'd be presenting it for a Nobel Prize rather than rep on SE. – ApproachingDarknessFish Jul 21 '16 at 1:04

Since at the moment of core collapse and implosion a Type Two Supernova can outshine an entire galaxy of 100,000,000 stars, you have a pretty tough job ahead of you.

The obligatory XKCD comic gives you a taste of what you are in for, holding a thermonuclear device to your eye would have nine orders of magnitude less radiant energy than a Supernova exploding at the distance of our Sun from you.

With that sort of energy output, even using super science to put a Jupiter sized planet between you and the incipient Supernova isn't going to do much good; the cremated remains of the "shield planet" will strike your planet as a hypersonic cloud of plasma (the size of Jupiter) moments before the shockwave arrived to sweep away the mess.

This article suggests that the shockwave is coming at you at 8 miles per second. That is relatively slow compared to the monster outpouring of energetic radiation that has already swept through your world at the speed of light after the core implosion, but it will do a fine job of pushing the plasma left behind by your planet out of the Supernova's remnant space.

I suppose that some sort of metamaterial could be devised to refract the energy of the supernova around your planet, but the issue here is the amount of energy is so extreme that even absorbing the most miniscule fraction of the energy will damage the device, and once parts of it start to melt/vapourize, the rest will rapidly follow, and your planet for a fraction of a second thereafter.

The other issue is that metamaterials are optimized for particular frequencies, whereas the Supernova will be emitting energy over a very broad spectrum of frequencies, from long radio waves to intensely energetic gamma radiation. You can expect the same sort of thing to happen if you try to erect a massive mirror between you and the Supernova. Even a dielectric mirror reflecting 99.99999% of the light will rapidly vaporize and of course the mirror is not going to be reflective in all wavelengths either.

No, the only real way to save your planet when the core destabilizes and collapses, triggering the Supernova, is to not be there. Use your super science to create a wormhole and put your planet through it to another Solar System with a stable, quiet star, or use some sort of space warping geometry like an Alcubierre drive to get your planet out of the way post haste.

If you had come to me with the problem a few million years earlier, there is the possibility of stellar engineering to prevent the Supernova happening in the first place. The massive gravitational pressure of the star is compressing the core and burning through the hydrogen at a furious rate. since much of the hydrogen has been consumed and converted into Helium, the gravitational pressure of the star is allowing Helium fusion to take place, and moving up the curve of binding energy to heavier and heavier elements. When the fusion reactions create Iron (Fe) the process stops, since Iron creates no net energy when fusing (or fissioning, for that matter), so the gravity of the star is no longer opposed by the energetic output of the fusion reaction at the core: the star implodes creating the Supernova.

Using a technology called "Star Lifting", a great deal of matter could have been "lifted" from the outer layers of the star, reducing its mass and placing it lower on the Hertzsprung–Russell diagram. The extra mass could be stored in a series of artificial gas giant planets and used to fuel the star in the far distant future, or to do other things in the here and now. Based on the description, the star is already close to collapse, and I'm not entirely sure what would happen if large amounts of mass were suddenly removed from an unstable star. I'm not really willing to try that experiment, are you?

Using artificial magnetic fields to pump solar plasma from the stellar poles

• Comments are not for extended discussion; this conversation has been moved to chat. – Monica Cellio Jul 19 '16 at 15:55
• I am very late to the discussion, but would a Einstein-Rosen bridge like the one described in this answer, with one side between the planet and the supernova, and the other side on the opposite side of the same supernova cancel out the energy being released like in Nathaniel Ford's comment ("...If we can warp the planet out, can we warp in energy heading in an opposite direct from another exploding star?")? If the energy is spherically symmetrical, it should cancel around the planet perfectly, right? Use its own energy against itself? – Lord Farquaad Dec 4 '17 at 19:50
• @LordFarquaad did you use an Einstein-Rosen bridge to escape from the dragon? – walrus Dec 6 '17 at 23:15

This isn't a supernova problem. This is a pointy-haired boss problem, and it gets much easier once you realise that. So, "we are going to have to move the planet a bit, but that will minimise depreciation on the hardware." We're going to move it further from the star, but we are going to keep it in orbit around the star, so we are not running away. Since it's at least eight times the mass of the Sun, we can stand a long way back - at least three light years - and still be in orbit.

Call it 200,000AU, which means the damage from the supernova will be reduced by a factor of 40 billion, as compared with being in an orbit like Earth's. At this point the damage is about a fourtieth of having an H-bomb go off next to you. That means you can build a shield for your planet out of all the other planets in the solar system, and potentially have it actually work.

• Made me laugh. Very creative answer. Not the thing that I expected tough, but is acceptable afterall since it seems to pass all the established criteria. – Victor Stafusa Jul 17 '16 at 0:24

Create a pocket dimension and move your planet in there. During the nova, make the entry to the pocket dimension (that is, the size of it as seen on the outside) small enough that the energy that enters is no larger than the planet can handle. After the nova, you can widen the entry again and get your planet back into normal space.

• This is the only answer that could work, I think. – wizzwizz4 Jul 16 '16 at 12:13
• ...and then promptly freeze to death. – Telastyn Jul 16 '16 at 21:58
• All hail The Doctor. – Vincenzo Oliva Jul 16 '16 at 21:59
• Not sure if this is valid physic laws (don't looks like), or just a disguised "use handwaved magic" answer. – Victor Stafusa Jul 17 '16 at 0:34
• @VictorStafusa: Well, the hard-science answer would be: Forget it. – celtschk Jul 17 '16 at 8:02

### A question of scale

Supernova are powerful, extremely powerful. Imagine the most powerful explosion possible. Supernova are more powerful than that. Xkcd has this important note about how powerful supernova really are:

However big you think supernovae are, they're bigger than that.

Here's a question to give you a sense of scale:

Which of the following would be brighter, in terms of the amount of energy delivered to your retina:

1. A supernova, seen from as far away as the Sun is from the Earth, or

2. The detonation of a hydrogen bomb pressed against your eyeball?

A: the supernova by $1 \cdot 10^9$ times!

### Can planets even survive?

Earlier a question was asked on this board: Can planets survive a supernova explosion?. I recommend reading the answers.

In summary, if a planet is sufficiently far away, then some planets could survive. For instance, if you placed Jupiter in orbit around a star about to go supernova (Type II), then there is a very good chance Jupiter would survive.

At Earth's distance, the Earth would not (then again, Jupiter probably wouldn't either).

There's only been a four planets found around pulsars (supernova remnants). Of those, we think that only one was present before the supernova. However, this "planet" started as a star. The "planet" that is left is the star's carbon core. The supernova blew the rest of the star away.

### But could people survive?

Let's assume the planet is far enough from the supernova to prevent its vaporization and placed behind some other object (like another star) to protect its fragile surface from being blasted into space.

Even then you need to worry about a lethal dose of neutrinos. The XKCD link above states that you need to be a minimum of 2.3 AU away from the supernova or the neutrinos will kill you regardless of the number of stars you use as a shield. In fact, you'll want to be significantly further away than 2.3 AU or large fractions of the population will die from the neutrino flux.

### Yes, you can save the people

But you'll need to:

1. Move the planet as far from the star as possible. Probably 5 or more AU away and further is better.
2. Place another object between the supernova and the planet to shield the planet from the normal radiation blast. A big planet is a minimum, a big star would be much better.
3. There are still no guarantees.
• @VictorStafusa Computers are vulnerable to radiation. Anything with small enough parts is. – hyde Jul 16 '16 at 5:46
• @hyde how about these old room-sized computers that don't have any small parts? – John Dvorak Jul 16 '16 at 7:09
• @JanDvorak I guess you could work with that, but in computing "no small parts" means "large distances between parts", which means "slow and needs a lot of power". I guess you could come up with some alien computing technology, which makes the whole premise still worthwhile. – hyde Jul 16 '16 at 13:31
• @Jim2B Note that surviving the initial blast is not enough. As calculated in this answer, next few months will be like being inside a supernova strength gamma ray oven. You have to shield your planet from all directions somehow, or you can expect large parts of it simply be vaporized by incoming energy flux. – hyde Jul 16 '16 at 13:41
• Others have calculated that the neutrino radiation is a much bigger problem that Munroe calculated. A 5 sievert (fatal) dose at 100 AU and a large cancer risk increase at 3 light years. This is due to more recent data collected from biological neutrino interactions measured from a nuclear reactor. – Gary Walker Jul 18 '16 at 4:23

a) they want to maximize energy extraction from the supernova,

b) their equipment can't withstand a supernova.

Short answer: shoot the management, evacuate, come back when they have a clue

• Funny, but that is not really the answer. :D – Victor Stafusa Jul 18 '16 at 9:38
• @Victor Stafusa: True but therein lies your answer. You need an energy sink that can absorb anything the supernova can throw at it. Then connect the sink to something with a lower potential and draw out the energy at your convenience, much like charging a battery. This changes the two complementary problems to just one: designing your Dyson sphere to absorb the energy of a supernova, faster than said supernova can expel it. Having a planet in the way does nobody any good. Even the mice left when the Vogons showed up – nzaman Jul 18 '16 at 13:47
• @VictorStafusa It absolutely is the answer though. You cannot simultaneously get the energy you need to collect without accepting the consequences that much energy demands on you. – corsiKa Jul 18 '16 at 15:32
• @corsiKa Agreed that you need to collect the energy and accept the consequences, even if those two goals seems to be incompatible and unreconciliable. However this answer says that the solution is "shoot the management", which is something completely different (even if we can also agree with that). – Victor Stafusa Jul 18 '16 at 21:20
• @VictorStafusa Nope. This answer is not "shoot the management". Yes, those words do appear, but it is quite clearly tongue-in-cheek and not the actual answer. I'm starting to see where management gets its ideas from... – corsiKa Jul 18 '16 at 21:37

The interconnected sea of Higgs Bosons constituting space time has some properties of non-Newtonian fluids. Normally, the linked bosons provide the "medium" which propagates interactions between different points in space time with the speed of c.

But excited by a specific resonance frequency of gravitational vibration, the bosons stop interacting conventionally. Space time starts to resemble a friction-less super fluid. Interaction between different tempo-spatial locations are near-"instantaneous". A plane of such an anomal "super-fluid" space time would act like a shield from events like supernovae on the other side of it. Leakage from the plane is minimal; all events are propagated with high preference inside that plane, much like electrical charges travel inside a conductor. The effect can be visualized as a spatial-temporal Faraday cage.

Conveniently, the events (and the energy they carry) leak at the edges of the plane where they can be harvested, for example to carry out computations.

The details are rather tricky: Close to the plane's edge time and space do funny things (let me say that the tidal forces are your least worry), so that you want to keep a healthy distance. The plane must be large to shield the planet effectively; the energy pouring out at the edges partly radiates inwards, and it's a lot. Creating a super fluid Higgs Boson field of that scale requires a large amount of gravity resonators placed at very precise locations in order to create the required wave form.

It also requires an inordinate amount of energy which would plainly not be available under normal circumstances. Luckily, the supernova will provide plenty, which can be used to bootstrap the field at the moment when it is needed. The engineering problems are enormous, but they are just engineering problems; I'm sure you'll solve them in time.

• I think that I am too dumb to fully understand your answer, but it is a very interesting one nonetheless. I will need some time to digest it. Anyway I think that claims like "But excited by a specific resonance frequency of gravitational vibration, the bosons stop interacting conventionally" needs some citations. Also, does "Interaction between different tempo-spatial locations are near-"instantaneous"" imply the existence of some sort of faster-than-light phenomena other than quantum entanglement wave-function collapse? – Victor Stafusa Jul 16 '16 at 20:12
• @VictorStafusa This answer is technobabble as far as I can tell. – March Ho Jul 17 '16 at 6:09
• @MarchHo Yes, it is "technobabble". I tried to find a hook in known physics (Higgs Bosons) where very advanced physics might find interesting things. If we know more about what constitutes space-time, we may or may no find interesting properties of it. – Peter - Reinstate Monica Jul 17 '16 at 10:25
• @Victor Stafusa it is absolute technobabble, worthless as an answer. Absolutely meaningless. One wonders if the poster is just ridiculing you. – Justin Thyme Sep 29 '18 at 0:23
• @JustinThyme So you criticize one answer of me as unimaginative and this one as, if I understand correctly, overimaginative. You do realize that the OP asked how to survive a supernova, an event that will kill you, famously, just by its neutrino radiation. Paraphrasing a common scientific principle: Bold problems require bold concepts. Of course this is technobabble, if you want to use a derogatory term. This is an SF question, not an S question. – Peter - Reinstate Monica Sep 29 '18 at 1:05

My dear friends, worry not! Your planet will be safe, your religious rituals will be fulfilled, and you will be able to collect plenty of data should you chose to do so on a whim ;)

You must construct a massive object, known to us as a black hole (even better would be a charged black hole). Use the fundamental forces of nature, gravity and electromagnetism, to maneuver this black hole precisely between your sacred planet and the star. Use thrusters to maintain your planet at some distance from the event horizon, while still being in the umbra of the black hole. You may worry that this will obstruct any data coming from the star, but you are mistaken. Gravitational lensing will ensure some of the radiation coming from the explosion will reach your receptors. The further away you are from the event horizon, the more of this data you will receive. You can fine tune your position so that you get as much data as possible without being annihilated.

If you are worried about the gravitational effect of the back hole interfering with the supernova itself, you can always move your planet and black hole back a little but (not run away, but maybe a couple more AU's)

• Gravitational lensing - exactly why using BH is't such brilliant idea. Shadow cone will be not geometric one. Depends trough on size of that BH but 10 solar masses is just 30 km radius. And that 10 solar masses near star might unpredictable to disrupt processes in star make explosion more asymmetrical and make things even worse for that particular direction. (hm, up for you thinking about that, but it might be not so easy - Jupiter affects Sun pretty noticeably from 5a.u. distances with 0.1% Sun mass) (sun cycles might be connected with $\small \sim$600km offset barycenter movements) – MolbOrg Jul 17 '16 at 18:30
• @MolbOrg Hm the radius of the black hole is a problem. But maybe the event horizon is a few hundred km think? I haven't been able to find a good source for the thickness of the event horizon. Also, maybe the aliens decieved us even more (to make the religion story more credible), and the the "planet" is just an asteroid a dozen km accross. Also, maybe they can adjust mathematically for the BH's effects on the supernova, or they can move 100-1000 AU away from the star, which is still quite close for a supernova – Ovi Jul 17 '16 at 19:06
• The bad side is that gravitational lensing would also lense supernova's radiation towards the planet. If we move the planet to be near enough the BH so the lense would focus significantly far away to the planet, tidal forces would desintegrate the planet making it be a ring of accretion around the BH spinning at relativistic speeds. For it being large enough to create a large enough umbra without destroying the planet, it will need to be a supermassive blackhole... – Victor Stafusa Jul 17 '16 at 20:22
• ... However, if I have enough energy to maneuver a supermassive blackhole, then I would probably not need the supernova afterall, since it would be far easier to just use that energy instead to directly decrypt the data. Further, relativity will mess that idea in strange ways. – Victor Stafusa Jul 17 '16 at 20:24
• @Ovi no, not hundred, size of BH is measured by event horizon, we do not know what is inside in with form etc, measuring arbitrary outside also makes no sense. Size is event horizon. There is no thickness - it's singularity or it's inside or it's outside. If greater distance is solution there are easier then BH approaches for that. – MolbOrg Jul 17 '16 at 21:21

"The aliens need to keep the planet around the supernova. In fact, they are interested in this planet exactly because the star will explode as a supernova." This suggests that if the aliens want to keep their planet in orbit around a supernova they must have (a) a good reason for doing so, and (b) some way of using this to their own advantage. What (b) suggests is that the aliens already possess the technological means to save their planet.

This message is just a test to see how smart we are. Basically it's a trick question. To determine if we can work out that they don't need our answer to save their planet. OK, aliens if you can do it, then just do it and stop pestering us poor Solar3alings for no good reason.

There is a very simple solution, and won't require that much energy (in comparison with some of the answers).

Warp the spacetime continuum (like alcubierre) somewhere in between the star and the planet, in such way to divert all radiation/neutrinos/plasma/garbage/etc away from the planet. (And away from the warp-machines, of course).

So... basically a big gravitational lens/shield.

• I liked this. Very good and very simple. – Victor Stafusa Jul 18 '16 at 22:40

Supernovas are unimaginably violent and energetic. So far as we know, no planet can realistically survive one. Meh, no planet in a goldillock zone can even survive a red giant star-phase. To do an impossible task, you must also possess impossible impossible power and skill. So then, with far, far futuristic technology, you have these options.

# Method 1

One method to survive the supernova is to not let a supernova occur at all. You can:

1- use an immensely massive rocket engine to push your planet away from the parent star. Then bring in a small white dwarf to the parent star so that they are as close to each other as possible, without colliding into each other. The white dwarf, being superdense, would have far stronger force of gravity than the parent star, and would suck in material from the parent star. However, if white dwarfs suck in too much material, they can themselves explode in a supernova. So when the said white dwarf has sucked in just enough material, move it away from the parent star and bring in another white dwarf. With a few dozen such visits you can remove the mass of the parent star enough to avoid any risk of supernova at all. Now use the immensely massive rocket engine again to bring your planet closer to the parent star.

2- explode away huge chunks of your parent star using anti-matter bombs. Basically you want to fling anti-matter packets at the parent star. Once they hit the star, they would annihilate to create millions of hydrogen bombs sized explosions (matter and antimatter annihilate on contact and result in an Einsteinian explosion of $$E = MC^2$$). Explosions of this scale occur all the time in the core of a star, but are suppressed by the monstrous gravity of the star. On the surface, there would be nothing to contain or suppress them and huge chunks (upto the mass of half an Earth or so) of the star are torn away with each such event. Make sure to cause these gargantuan explosions to the other side of the star from your planet (the side facing away from your planet) so that your planet doesn't get swept clean by the ejecta. Once you have successfully blown away enough mass of the star, you have circumvented the danger of the supernova altogether.

# Method 2

Move your planet faaaar away (at least a light year away) from the parent star. You would have to subsist on your own generated power on the planet as no stellar energy would be available. But with your exaggerated level of technology, this should be easily obtainable. Once the star has exploded and the debris settled, move your planet back to where it used to be.

• they wish explode to happen - they interested at energy or something in that explosion. and it will not work with dwarf - dwarf is't super dense and comparing to host star is too small his orbit will decay(with mater exchange) and he will eventually sunk in host star. Also I highly doubt that it will consume matter, instead being consumed by host star. To answer that Q you have to move from Supernovas are unimaginably violent and energetic. to I know the number. – MolbOrg Jul 17 '16 at 18:09
• white dwarf 8-10 mass sun, and that is lowest boundary to go to supernova - so this star will be more massive probably. But yes it might work in some circumstances - but to slow. – MolbOrg Jul 17 '16 at 19:04
• The method 1 is just to prevent the supernova, which is not a way to go (the challenge is to survive a supernova, not to escape or prevent it). Method 2 is acceptable, but John Dallman already posted an answer on that before. – Victor Stafusa Jul 18 '16 at 9:42

Can you create an artificial black hole? Take one of your planets and collapse it into a singularity, and then launch it into the center of your sun?

My limited understanding of supernova is that the outward explosion is a result of an inward collapse as fusion comes to an end, thus initiating a much more rapid fusion which counteracts the collapse, and sends everything flying back outwards.

I don't know the math to do such calculations, so I don't know the net result. I see multiple possibilities:

1. The inner mass gets sucked into the black hole. The fusion gradually peters out as it loses density. It causes a gradual collapse of the outer star, eventually sucking the whole star in, but the energy released from the accretion disk is absorbed by the surrounding hydrogen. This is the effect you are searching for.

2. The mass gets sucked in so fast, it terminates the star's fusion, the whole thing collapses inward, but the black hole's force isn't enough to collapse the outer layer before a rebounding shockwave in the middle regions (between the black hole and the remainging outer shell) triggers the supernova prematurely.

3. The black hole just sucks in everything in as it gets close, and the release of energy blasts apart the system more intensely than the supernova itself.

Maybe other possibilities I haven't thought of. Anyway, I suspect that the exact effect is going to be determined by how large the black hole is, how fast it is moving relative to your sun, exactly where it hits and the angle of incidence, and who knows what else. If you consider this an option, I strongly recommend you run as many simulations as you can, if you do it wrong, you're liable to make things worse.

Another option with a black hole would be to make it graze the outside of the sun rather than entering into it. If you can put it in a close but stable orbit, maybe it could extract mass gradually enough that it won't trigger a supernova, and might even leave a small star behind at the end. Again, run a lot of simulations of this scenario before attempting it, don't just guess. There's so many things that can go wrong.

It's still going to be releasing unimaginable amounts of energy as matter gets pulled in, but hopefully you can end up directing a good chunk of it inward to the black hole instead of in your direction, and hopefully it will be a lot more gradual than a supernova.

[When I say "you should run a simulation", I'm talking about the aliens in this situation, who should obviously have the computing power to do so.]

• Yes, you can create an artificial black hole. – Victor Stafusa Jul 16 '16 at 21:20
• There's one small problem with this solution. A planet Earth mass black hole is the size of the full stop at the end of this sentence. It has a fairly small intake area to consume stellar matter and allay at any upcoming supernova. The flow rate won't be enough to bulk this miniscule black hole to a size big enough swallow sufficient mass to make a difference. Also, it will take a long time to do so too. Otherwise it's a cool idea. – a4android Jul 17 '16 at 9:31
• Interesting... I just did some basic calculations on how fast a black hole the mass of Jupiter would absorb matter in our sun's core, I came up with an order of magnitude 10^9 kg/s, which sounds like a lot, but the black hole would take tens of millions of years to double in size. – Bryce Wagner Jul 17 '16 at 13:44
• I assuming most of the absorbsion is going to be from influx of 500km/s plasma with a density of 1000 kg/m^3 (10^30 particles per cubic meter from en.wikipedia.org/wiki/Plasma_(physics), and 1.6*10^-27 kilograms per proton. The surface area of the black hole will be about 8.3 meters, so my round estimate is 4.8*10^9 kg/s, which could be off by an order of magnitude. I think the acceleration due to gravity of the black hole would be negligible in this scenario until it grew much bigger. – Bryce Wagner Jul 17 '16 at 13:53
• @BryceWagner something aroung +25km/s at the end - density of media can be bigger star core density and sped will be bigger in core - so if you drop it without angular momentum at 1a.u. - it might stop and be in core after reasonable mount of osculations(at least it might speedup things) but yes overall for small holes they are not astonishing fast in consumption. – MolbOrg Jul 17 '16 at 17:58

This is a community wiki "non-answer" to summarize answers that won't work, at least not without some severe modifications. Feel free to edit this if you wish.

1. Move the planet to somewhere else very far away: This qualify as "just running away" which the OP specifically tried to reject right from the start because it is the easy non-interesting obvious solution. Coming back later does not makes this any better. Replacing "somewhere far away" with "inside a hidden dimension" or something like that do not makes it really different.

2. Preventing the supernova from happening: Also something that the OP specifically rejected right from the start because it makes the challenge uninteresting. Making a black-hole swallow the giant star prior to its explosion would not also make it any better either.

3. Use magic, unrestricted time-travel as in Back to the Future movie, faster-than-light communication, TARDIS, unobtainium adamantium shielding, technobabble, etc: If you are inventing your own physics, then every answer would be possible, making the challenge uninteresting and closeable as too-broad. So, this is not valid.

4. Putting a massive planet or a smaller star as a shield: It would work to shield the planet from the initial blast (except for neutrinos). However, as the supernova quickly erode the shielding object, its debris would obliterate the planet. Anyway, this could be workable with some modifications.

5. Putting a neutron star or a black-hole as a shield: Black-holes and neutron stars are tiny (measuring a black-hole size by its event horizon radius). They features only several kilometers in diameter, so they are too small to shield the planet. Further, their gravitational lensing would focus a lot of radiation from the supernova on the planet. However, some modifications to this setting might make this workable.

6. Using a very large black-hole: If you get a very large black-hole to shield the planet, it would probably be at least an intermediate mass black-hole or a supermassive one, and it would very likely promptly swallow the giant star preventing the supernova or perhaps spaghetifying it to the degree that it becames an accretion disc. Again, some creative modifications to this setting might be workable.

• Speaking as someone who used time-travel for an answer. I will say I didn't invent my own physics. Time-travel via wormhole is an established scientific concept. Now whether time-holes or wormholes could exist is an open question. This is legitimate speculative physics that does not violate the laws of physics. It is not unreasonable to assume they exist and for an exercise like this to choose the wormhole model with best fit. However, I do agree with the other non-answers on your list. – a4android Jul 18 '16 at 4:43
• You mention neutrinos above. Since there is no possible matter or mechanism capable of shielding neutrinos and black holes are absurdly difficult to do anything remotely sensible as a shield, then there can only be one answer. Bob Gray's large wormhole or Einstein-Rosen bridge, perhaps it might need to be bigger. Speculative physics, yes, but within reason it does the job. The neutrino problem is fixed too. And it's not on the non-answer list. – a4android Jul 18 '16 at 4:52
• The best thing about the non-answer list is that the OP has clarified the ground rules for any answer. I wish more OPs would do the same thing to give an idea what criteria they applied in selecting their preferred answer. Too often, I have seen OPs choose an answer when other answers were better choices and I couldn't understand why they did so. A non-answer list would have helped. The OP didn't initially exclude exotic possibilities of physics, so they can be in play. – a4android Jul 18 '16 at 6:50
• @a4android Oh, sorry. I meant time travel like in the movie "Back to the Future". I'll edit to clarify that. Anyway, I think that wormholes are great, but if we can find a solution without relying on them, it would be better. Anyway I'm waiting for some answer that solves the issue nicely and creatively without the needing of too much speculative science. If none appears, I'll look for the best answer and accept it anyway. – Victor Stafusa Jul 18 '16 at 8:04
• Victor, your clarification is much appreciated. I really like your non-answer list. It gives feedback to WBers and helps set standards for answers. It would be great if it was done by more OPs. Your problem sets a high bar and speculative science may be the answer. I had an inkling of another solution, but neutrino radiation would still kill it dead. Alas! – a4android Jul 18 '16 at 13:29

Hmmm, here's an interesting thought:

Create a station in-between the planet and star with enough motive power to maintain position against the nova shockwave. Any potential motive output will need to be offset so that it does not interfere with the planet. It will need shielding to protect it's functioning parts from not only the shockwave, but also the energy output, and any stray chunks of stellar crust or core that may happen its way. It may also need something with enough mass to stop or deflect heavy particles which tend to ignore most objects with mass. It might need to be big enough to physically shield the planet from the nova.

The primary function of this station is to generate, store, and emit massive amounts of anti-matter of various types. it will create a fountain of anti-matter, centered by a high pressure "spear" of anti-particles. Impacting the material of the nova will create continuous large explosions which will have the effect of parting the wave of the nova just in the vicinity of the planet. Remember to allow for the angular momentum of the planet's orbit, unless it is planned to temporarily halt the planet. Addendum: the motive source of the station needs to be powerful enough to not only withstand the pressure of the various waves a nova will generate, but also the long term emission of anti-matter, and the subsequent motion imparted by the matter/anti-matter reactions over time and remain functionally operative over time.

It is possible to generate anti-matter now, and even store it for short amounts of time with our existing technology. An advanced tech-base should be able to do much more with the concept. Don't point the station at anything you want to keep, and don't let just anyone have the keys.

Ever given any thought to ah, just picking an example at random mind you, building a dyson sphere around the sun at a distance likely to survive the output and then to just relocate the planet only far enough to put it just outside the dyson sphere and then hooking it into the power and sensor net of the sphere? Great way to store up extra energy, plus to avoid having your neighbors laugh at you for losing your sun, you could even have the sphere emit in the exact same spectrum as the pre-nova sun for quite a while. Just wondering.

Oh, and according to some of our greatest thinkers on our planet, the answer is 42. Just in case you hadn't found that out yet.

• If the shockwave is enough to obliterate entire planets (Earth, for example, would entirely vaporize down to the inner core and be completely blown out as hot plasma in less than a day). So, how could the station be shieled in order to maintain its position and survive the explosion without it being at least a larger planet by itself? Also, since there is a dense and powerful spray of matter particles coming out everywhere in every direction, there is no way to intercept all of them as they're flying. Further, anti-matter anihilation will release even more energy around to just make it worse. – Victor Stafusa Jul 18 '16 at 22:38
• The fountain shape of the antimatter stream will cause an umbrella effect. A nova or supernova will primarily move outward from the point of origin in a spherical manner. Unless this shockwave hits something, such as a neighboring planet, there will not be a lot of sideways movement in the waves coming from the star. With the umbrella effect generated by the ongoing fountain effect of the station, plus the heavy particle shielding, this will create a vacuum shadow where there is not a lot of radiation or stay particles behind the station, where the planet is. – nijineko Jul 18 '16 at 22:47
• But I think that in order to provide enough antimatter to create the umbrella effect, you would need a so large anti-matter mass that it would be at least an anti-matter planet as a shield (possibly as large as a smaller star). When that is anihilated, I am afraid that it will release so many neutrinos, gamma rays, light, heat, glow, radiation, etc that it will outshine the supernova, making it still worse than just letting the naked and abandoned planet to take the direct supernova hit. – Victor Stafusa Jul 18 '16 at 23:15
• Well, it would certainly be bright, but the point of anti matter is that it would not produce many post reaction particles, it would cancel them out. Also, the shadowed planet would be mostly protected, except for what energy it is absorbing. Then again, if there is still a lack of confidence, there is always the Dyson sphere idea. I was going for novel and different from what was previously suggested. The anti matter fountain spear would be a spectacular method. And presentation is key. – nijineko Jul 19 '16 at 1:44
• I agree that your answer is different than everybody else and I like your idea - it is very inspiring. However, it still don't looks right for me, I should think about it carefully for some time. – Victor Stafusa Jul 19 '16 at 1:58

I've done my funny answer now it's time to roll up my sleeves and get serious. Fortunately, everything needed can be found in the answers of my esteemed colleagues.

Starting with Bob Gray's Einstein-Rosen bridge, but to start with it won't be inflated to its full size of two planetary diameters as that will come later. An Einstein-Rosen bridge was the first version of what we today call a wormhole. The original Einstein-Rosen bridge will be traded in for an Ellis-Bronnikov wormhole (also known as Ellis wormhole for short) with Gauss-Bonnet gravity conditions. Because no exotic matter is needed to keep it open. All the details about this type of wormhole can be found under this rock.

Youstay Igo's immensely massive rocket engine will be fitted into a high-acceleration long-range interstellar spacecraft. This vessel will transport one mouth of the Ellis wormhole. It is launched with an acceleration of one thousand gravities. If an immensely massive rocket engine can move a planet propelling a spaceship at one thousand gravities should be trivial.

The vessel is sent out into deep space. Its acceleration will produce a large amount of time dilation which once achieved the ship will coast at near-lightspeed velocity deep into the galaxy. Travelling for several thousand light years away from the supernova the vessel will be unaffected by its radiation and blast waves. Once it is sufficiently far enough away the ship decelerates then turns around and accelerates on a return course to the supernova.

Entering the shattered ruins of a planetary system obliterated by the awesome power of the supernova. At last it goes into orbit around the neutron star that is all that remains of the exploded star. The Ellis wormhole is deployed and inflated to its full size of two planetary diameters.

Several thousand years earlier, a few years after the vessel screamed out of the planetary system at an acceleration of one thousand gravities, the aliens inflate their end of the Ellis wormhole to its full size of two planetary diameters. The huge time dilation means if the aliens peer through the wormhole they will see the remains of the supernova several thousand years in their future.

All they have to do now is allow their planet to pass through the Ellis wormhole and emerge in their own future. Now they are several thousand years in the future. The worst effects of the supernova are now long one. It is safe for their planet to once more take up residence in its own orbit again.

Actually it will be away for as long as it took for the planet to pass through the wormhole which at two planetary diameters won't be too long at all. No more than a few hours. This assumes a velocity of about one km/sec in passing through the wormhole. The planet won't have run away. It has simply moved itself into the future of the post-supernova and it can get back to business again. Admittedly there will be a service interruption of several thousand years, but that's not unusual as we've all had ISPs like that.

If that doesn't work, and there's no good reason why it should fail, but this is a further safeguard. Keep Charles Rockafellor's planetary diameter sized black hole. Because a black hole big enough to shield the planet would be big enough to drop into the star and consume it before it has a chance to go supernova. Then the planet ends up orbiting a black hole.

There you go, two solutions to the one problem, so you can't say fairer than that. I am grateful to my colleagues for their creative ideas which provided the conceptual leverage to save a planet from extinction by supernova.

• I don't think that I really understood this. Looks like that you are trying to use time dilation and a wormhole as a device for traveling through time to the future. – Victor Stafusa Jul 18 '16 at 1:02
• Exactly! This is a well established concept in general relativity. See Wikipedia entry above. Wormholes as time machines like this is so commonplace idea I didn't think it needed explaining. My bad! Basically moving one mouth of a wormhole at relativistic speed means time dilation for moving mouth creates a time difference between the two mouths. Step through the stationary mouth & you're in the future. Speculative physics at best, but it does solve the problem without leaving any unintended loopholes that might destroy the planet. – a4android Jul 18 '16 at 1:30

This does not fit into a comment and some points are valuable as an answer, so it's kind of a clarification for A above.

A hard sphere is bad, no no, it has to be not hard, it has to be flexible. More than that - it has to be active and actively interact with the shock wave, and extract energy.

Shock wave speed is around 20'000km/s. So the sphere has to have a more complex structure then just a plain sphere. It has to have some inward parts, which will accelerate to that speed in the direction of the wave, and shape the incoming wave. And with the interaction of the shape areas of the wave, without destruction of those parts (the parts which interact with the wave, have the velocity in direction from star, heading to the outside of the sphere with relatively same speed) - jets inside jets, to let areas of the wave pass the main grid (slip in-between) and begin to extract kinetic energy, heat energy from that shock wave. (The extraction has to begin even earlier, at that shaping wave time, with de-accelerating and accelerating again part which was moved to star.)

• Yes, I did not forget about conservation of momentum, but it's the best way I could to draw a picture.
• Funny note: if you will hover near planet - not orbiting, you might spend GG of fuel and fly nowhere, be still around the planet. Not so easy, but just a funny note.

A of a25bedc5-3d09-41b8-82fb-ea6c353d75ae is a good answer because it suggests an energy extraction mechanisms for that whole situation.

Also QC of those aliens, it can't be on the planet. It's just a question of efficiency. If they have reversible bits energy, they maybe do not need much of that supernova energy. If they consume and dissipate energy in the process of making calculations, placing this computer on the planet makes no sense - it can't consume that energy in a reasonable time, to make calculations of that size.

More than that, they might use the supernova blast and for energy and for building that super QC system. They will have plenty of material, rich with heavy elements, in volumes hard to find in other parts of the universe and more importantly, hard to collect in one place (takes a long time, or special circumstances, like a super massive black hole in the middle of a galaxy).

Even more important than energy is a possibility of having a black hole (if the chosen star is good) as the result of such explosion. Using which it is possible to extract energy from the matter they can obtain in the location - around stars and from remains of this star and other star systems. Matter of energy conversion could have a good efficiency like $\small 0.5 \times mc^2$(if my calculations and assumptions are correct) and potentially have a much greater yield than the explosion of supernovae itself over time.

And those objects (Supernova remains + BH or NS) are valuable resources, so even if you have one, you might want to have more of them, and they are rare enough. This place might begin to be a place of force on a local scale (1000's ly) for them. Yes, you might get cold remains of such event of in the past, it will still valuable but could be a looong journey to power, but with all or most of remains of super nova it will be really very attractive place in therms of energy and matter, and it makes great sense to overcome all difficulties on the way to obtain it and handle the situation in more sophisticated way.

Those guys have an adventurer's nature: Everything that does not rip the universe apart, makes us stronger!

This way the supernova blast is indeed, great opportunity, which might be exploited.

This antimatter spear part also isn't bad too, might work, there will be a lot of radiations, but a shield for a planet might work too. No need to annihilate everything, just slight change of impulse to form a shadow cone. Move planet, all planets, probably rob near by systems for all heavy materials (from stars too) (not necessary), add more H He to the star to make it blast when you need it, not when it wishes(at least ability to tune process a bit, and capture more neutrons, easy to burn thermonuclear fuel is also useful stuff, not easy to make fast and in quantity).

Just a regular matter spear will work the same way as antimatter especially if you accelerate it to 20000 km/s(not necessary, just saves some mass in exchange for energy requirements) in case if you wish to protect a planet, and it is cheaper then antimatter, and easier to obtain. Same way as Ablation. So saving a planet as a bioreactor is possible. (also wave of matter from such blast is a plasma, thus using magnetic field helps to protect such spear and reduce its ablation losses)

Anyway, better to move the planet away, at 100'000 A.U., the same distance as the sphere, the flash will come in 1.7 years, the wave in 15-20 years. A sphere of that size can dissipate (at 1200K) (or convert to energy) Hypernova 1e46J blast in one year. Strongly suggest to read my answer about planet moving, "sphere" can be done such way.

Distance is good not only because energy density decreases proportionally to $\small \sim 1/r^2$, but also because blast wave is not energy-velocity monochromatic, so this way it will grow more gradual at a bigger distance.

Also, some separation of materials by atom weights might happen, because of acceleration mechanisms (light pressure and such), we do not need all elements equal, some we need first, and it's would nice to use the possible situation for our advantage.

Also, this way we might focus jets into nearby stars where we have also systems waiting for actions, by focusing shockwave into Hydrogen Helium jets(after removing heavy elements, and because we might not need light elements). This will focus the energy of the blast and allow star lifting using that energy when those jets arrive in star systems around. This way we might convert nearby stars to clouds (1000's of them) which we might to transport to our BH, later. Star lifting or complete disassembly and converting a star to a cloud by using the energy of a star itself is a million's million's year process and because of that using energy of supernovae in form of those jets to speed up the process is a good idea. There are also other tricks which could be possible with those jets, as redistribution of the impulse of that shockwave matter in jets and keep our shell momentum intact(or near so) which is one of the great problems in the situation. By using the energy of the incoming wave, to accelerate some part of it to let's say near 1c velocity. It helps to leave a significant portion of the matter from the star in its system, 98\% of it, and focus the energy of the blast in 2\% of the matter and near 1c speed, thus it will arrive to systems we would like to disassemble much faster, 50 times faster than it would be if we just focus 20'000 km/s jets as it is. Sure efficiency will not be 100\%, but it could be closer to that than one could expect in the situation.

This way we do not need to catch all remains at once, only part we can and need atm, everything else we will catch in other star systems. As a backup plan, if power exceed our expectations.

With the help of the BH and the stars around and tools, this wave can be stopped in reasonable time.

The remains of the supernova, in the form of a BH or maybe a neutron star, in worse case (or it just another possibility also good one, I even do not know what to choose neutron start(NS) or BH, give me both) will be a great help in stopping the wave.

Also, a great way is to launch expansion across galaxy at 0.99c speeds or fly to SMBH for goals like this answer Why would a civilization choose to inhabit a single enormous vessel instead of maintaining interstellar colonies?

So yes, supernovas and possibilities they offer are really attractive, but people plz plz do it well this time, not like it was with planets (ships searching planet with live and bananas to eat, 1960-70-80-...-novadays) - let's do it right this time))

Value of supernovas have to be noticed, senpai noticed you.

## Note

• A supernova starting from 10 mass of sun, so at 100'000 A.U. average amount of matter flow trough sphere from star will be 0.00704 kg/m2 (or one cubic centimeter of iron), and if wave will spread during 15 year of travel, in a way let say it begins at 15y mark and ends (kinda) at 16y mark - this value per second will be much less then that (just high speed dust), but more constant pressure. We might do a lot of things with that density flow at 20000 km/s or even more, even in case of hypernova (10 times more mass).

• One of your priorities is to isolate remain BH or NS as soon as possible, to prevent matter being lost in accretion processes. It's more important than even catching all of the shock wave, because it might make BH and NS inaccessible for out tools in the future, for a longer period of times then we might wish.

• Isolating and lifting matter around a BH (NS) is a great way to utilize some energy of shock wave, this way we may catch more and easier.
Again, clearing the area around the BH (NS) is important - it's our anchor for the operation.

• A spear is a good way to clear path to internal olume/guts of the explosion, shortly after the blast, before wave will come to soap bubble sphere.

• A sphere does not have to be tick, it's not a wall stopping shock wave - it's like mesh-net with soap bubbles

• 15 years is more than enough time to cool down for shock wave Supernova, Light curves.

• Very important moment, this Supernova, Energy output :

Only 0.1 foe (1foe=1044J) or less in form of gamma rays and other forms of radiation, even for hypernova, most energy is in form of kinetic energy of ejected mass.

• Another important moment, the result of the blast are heavy elements, and after some years they already below melting points, and to contain them in compact form, soap bubbles do not need to apply any force to do that. So even parts we did not stopped may be kept compact in travel, so we will catch them as single piece later

• More important we do not need soap bubbles, at all, just channels where we forming sticks from that shock wave media, yes, at 20000 km/s speed. Most of elements are Al, Si and below. R-process

• How big, by mass, would that sphere has to be?

Good question. In the "move a planet"-question, there was a pressure of gases, and sphere's used there are rather small, and they needed 1% by mass for active surface(shell) with 1bar pressure inside. The efficiency of the solution is better with size, so with 100'000 (30 million km) times bigger, it will be 1%/100'000, so 1/10'000'000 mass of the star. (Volume grows $\small \sim r^3$, thickness, and mass $\small \sim r^2$, so the mass of content grows faster than the mass of the shell.)

But in the case of supernova remains there is no pressure to contain (solids, with a high melting point, mostly, pretty cool after 15 years), we have just press dust into solid sticks fast enough, so even less than that. (Yes, we will catch them later, in nearby star systems.)

So exchanging one Gas giant for carbon in the star prior the blast (until there is some carbon and it didn't burned out) is a good idea and that's enough. So probably even no need to rob nearby systems.

Those sticks we pressed, they will need some help to collect together during flight and focus their force on near by systems to evaporate stars, and yes we have to add enough of active material to accomplish that, but I think we still good with one GG.

Probably we might even stop all sticks with one GG size of material of tool, but that is not so much important until we can focus them on near by stars.

• Hypernova are not so good, as I wished, they might implode without ejecting materials, not so good, we wish ejected material.

• 20'000 km/s is from Normal Type Ia:
An outwardly expanding shock wave is generated, with matter reaching velocities on the order of 5,000–20,000 km/s, or roughly 3% of the speed of light.

• All energy of the blast, all 1046J (hypernova) might be stored in form of kinetic energy around black hole(potentially, not sure about tool, BH 30km radius may be too small for tool to do that, will leak - too small BH, SMBH is better in that sense), but not around NS

## N.B.

• Do not sell or exchange information with them if they are farther than 2000ly away, and you have doubts you will get from them what you agreed for.

• Ask for 10% of QC power

• If they are closer then 300ly and the problem is let's say today(our time), sell it anyway(are trustworthy or not) ask for 30%.

• If Venus is disassembled and they are closer than 1000ly, ask for the whole system, they might solve what they wish and take planet if they wish, and sell in case if they trustworthy(but take a hefty price, do not be cheap in the case, in all of those cases).

• If they didn't pay after the event, it can mean 2 types of problem. One is big - they are not trustworthy, it will be The Pain, if even possible at all to get them from that system. The second problem is not a problem, needs to check plans.

• I will need some time to read your answer carefully, but I am intending to read and think carefully about it in the next few hours. – Victor Stafusa Jul 21 '16 at 1:19
• @VictorStafusa feel free to edit my english. – MolbOrg Jul 21 '16 at 2:36

There's only one formula for surviving a supernova--be where it isn't.

Either move your planet out into interstellar space, or move your star away. The latter approach will take some of the mass off the star and thus buy you more time before the big boom, also.

• I wrote the "gossip" part of the story just to discard/disqualify the obvious solution "just run away". The challenge is to survive the explosion without fleeing it nor preventing it. – Victor Stafusa Jul 16 '16 at 22:49

Put a series of stationary smaller stars aligned in both sides of the big star (or perhaps, instead of stationary, make them rotating all with the same angular velocity). Don't care about spending a lot of fuel and energy to keep a bunch of stars stationary in relation with each other in order to fight against gravity and extreme tidal forces (all those stars would themselves provide more than enough energy for that). You will probably need to interlace a series of disposable rocky planets featuring the best refrigeration technology possible between the stars in order to build hi-tech bases able to keep everything in its correct place. Also, all of that will significantly screw up the big star rotation and make it deformed and ellipsoidal and would significantly deform the smaller stars too, but who cares?

Behind the last of those stars, in one of the sides, put the planet to be protected, inside a series of concentric Dyson spheres.

When the central star explode, it will quickly erode the first star in each side, which will protect the following stars from the blast. The first star debris however, will erode the following stars, and as it erodes, it exposes the second star which will also erode exposing the third and so on. The intermediary planets are disposable and doomed. Since there is a lot of stars between the supernova and the protected planet, it will take a significant time for the supernova to erode all of them. Since the supernova will last only a couple of days, eventually it will be extinguished with hopefully enough spare stars relatively unnafected between the detonated used-to-be star and the planet.

The reason for placing stars in both sides is to make it gravitationally more stable, keeping the barycenter at the supernova star. Also, this would give the opportunity to build two survivable planets instead of one, so you have a backup if something go wrong with one of them.

The series of debris will emit a lot of heat and light, just as all the dust and gas present from the combined stellar winds of all of those stars. Also, at least a few debris will eventually hit the protected planet. All of that will significantly damage the planet, but still much less than the supernova impact. So, use the series of concentric Dyson spheres as ablation shields and use your best technologies to keep them in place even if they are severely damaged. Eject to outer space instead of towards the planet any parts of any Dyson sphere ablation shield that became in too bad shape to continueing being useful.

Also, whatever is kept in the planet, it will need to be veeeery resistant from the torrent of neutrinos constantly hitting it.

Finally, there still are no guarantees.

Note: Since I am the OP, I choose to not accept my own answer as correct. Please, beat my answer with something better. :D

A supernova explosion would annihilate any known form of matter, so a solution must involve not getting hit by the supernova. You could move the planet to a larger orbit to reduce the energy of the incoming blast to something manageable, but that feels like violating the spirit of the "no running away" rule to me. So if you can't block the supernova, and you can't move the planet, how could you survive the blast? Easy! Use the same principles employed by the Alcubierre drive to curve spacetime between the planet and the star so that there are no straight-line light paths between the two. The star explodes and the outward burst of energy and matter flows around the planet.

The quantity of spacetime curvature can be tweaked to allow for some of the matter and energy of the explosion to reach the planet (within the bounds of what can be shielded against), if the aliens need to do some data collection about the supernova itself.

• This is very similar to Physicist137's answer, which was posted first. Upvoted it anyway. – Victor Stafusa Jul 19 '16 at 7:59

Since you seem to be looking for hard science answers, one thing to note is that it was recently proven that what we thought was the minimum energy needed to perform computation isn't the lower limit. Your linked crypto thread is now out of date.

http://phys.org/news/2016-07-refutes-famous-physical.html

"Now, an experiment has settled this controversy. It clearly shows that there is no such minimum energy limit and that a logically irreversible gate can be operated with an arbitrarily small energy expenditure. Simply put, it is not true that logical reversibility implies physical irreversibility, as Landauer wrote."

Some of the limits of computation, how much you could theoretically do with a certain amount of energy are based on what appear to have been incorrect beliefs about information processing and entropy.

It will push the research towards "zero-power" computing: the search for new information processing devices that consume less energy. This is of strategic importance for the future of the entire ICT sector that has to deal with the problem of excess heat production during computation.

It will call for a deep revision of the "reversible computing" field. In fact, one of the main motivations for its own existence (the presence of a lower energy bound) disappears.

• Not really an answer, but I really appreciate the information and the insight and promptly upvoted this. Thanks. – Victor Stafusa Jul 18 '16 at 21:23
• BTW, I really appreciate the first paragraph of your linked article, containing the quote from Einstein: "Everybody knows that some things are simply impossible until somebody who doesn't know that makes them possible." - This is exactly the spirit of this question! – Victor Stafusa Jul 18 '16 at 21:25

If you live in the fictional universe of E.E. Smith's Lensman series create a hyperspatial tube (sort of an early version of a wormhole) between your solar system and another one. Put one mouth of the tube right in front of your planet so your planet will enter the tube. Place the other end of the tube in the other solar system at a location where the velocity and direction of your planet as it exits the tube will be exactly right for the planet to go into a nice almost circular orbit of the new star. Be sure that there are no planets in the new solar system in positions likely to destabilize the new orbit of your planet. And close the hyperspatial tube before your old sun explodes!

The Lensman universe also has lots of different types of force shields that can protect spaceships and planets from the ray guns of other space ships. It is possible that the ray guns are so powerful that they could vaporize planets and are as energy dense as exploding supernovae. Thus any force shields that could defend against such powerful ray guns might also defend and protect against a supernova.

The planet Tralle, or Trallis III, capital of a space empire, was defended by the fortress planet Onlo, or Trallis VII, that should have been about a billion miles away. The weapons on Onlo were designed to destroy attackers after they had nearly reached ground level, but I suppose that nearly ground level actually meant billions and billions of miles, since the planet Tralle was protected by Onlo. At that time both sides in the space war were capable of attacking target planets with multiple mobile planets at a time to smash into the target planets, so the weapons of Onlo must have been capable of vaporizing multiple planets simultaneously and almost instantly at distances of at least billions of miles. Thus it seems likely that the ray guns on Onlo were powerful enough to have an energy beam density at least equal to a supernova at equal distances. Since the government on Tralle could not 100 percent trust the garrison of Onlo to not turn against them, they probably had Tralle protected by a force shield strong enough to stop Onlo's ray guns and thus a supernova's energy.

The Lensman universe also has energy screens that can convert the cosmic energy in interstellar and intergalactic space and turn it into usable energy. It is possible that such screens could be adapted to convert the energy of a supernova into harmless and usable energy to power force screens to protect against any supernova energy that gets through the power converter screens.

What if you don't live in the fictional Lensman universe and your technology is limited to that which Earth Scientists in the year 2015 consider possible? Then your in big trouble!

If some form of time travel is possible, and if you dare to risk erasing yourself from existence, and other time paradoxes, go back in time millions of years and begin the process of slowly moving your planet tens of light years away from your star over a period of millions of years before it becomes a supernova.

Here are some discussions of planet moving:

And if it might take many thousands of years to move a planet's orbit a few million miles closer to or farther from the sun, it obviously could take millions or billions of years to move it light years away from a supernova. So if you just found out that your sun is going to be a supernova soon, you need to go back int time at least millions of years in a time machine to start the process.

• 100y maximum and u are ready to move planet. Also you might to use that hole entrance as shield for planet - just be behind that entrance. – MolbOrg Jul 16 '16 at 18:28
• Well, in fact all of this answer reduces to two possible solutions: "run away using a wormhole as a escape route" or "use a vaguely defined and left unexplained force shield". None of them are what I am willing to accept. – Victor Stafusa Jul 18 '16 at 9:27

It's time to build a world engine and surf the rainbow.

So what we're going to do here is create a world engine which will allow you to pilot the planet away from the Supernova at a rate which will keep you at it's edge in order to avoid being obliterated while simultaneously allowing for maximum data collection. The engine is going to be powered by the Supernova itself, and in order for the engine to function, the spool will need to be able to dynamically adjust to ramping fluctuations in potential energy.

You are also going to require a star capable of sustaining a life cycle on your planet. This star will need to be placed directly opposite the supernova approach vector. Both your planet's and the stars orbit of the supernova will need to be fixed so that the planet eclipses the supernova at all times. The engine will need to operate independently of the planet's rotation while remaining fixed in a single location. This is simple to accomplish with a dual frame setup, the inner frame fixed to the planet in equidistant points for even distribution of force.

Once all of this is accomplished, the supernova will supply the power needed to elevate the electromagnetic force necessary to create a planetary shield that will prevent radiation from cooking your planet. As a secondary application, the energy can be redirected into a powerful blast resulting in an equal and opposite reaction pushing the planet away from the expanding supernova. The excess power would be channeled into holding the star at it's fixed point by propelling it before the planet.

In effect, you will utilize the supernova as a wave, and surf the rainbow holding a torch ahead of you to light the way.

• I am not sure if I got your idea right, but it seems that the planet should be "surfing" at light speed or near that just to run away and bring a larger star with him, while some vaguely specified eletromagnetic force will in some unexplained way create a planetary shield to take the hard work about protecting the planet somehow. If I understood this correctly, it would be just easier to either run away before the explosion (not interesting) or just have the shield working before the explosion (but then you need to explain how this shield would work). – Victor Stafusa Jul 18 '16 at 22:50
• Why would a supernova occur at light speed? Sure it's an explosion, but it's still matter being ejected, not just light. Particles have mass, and as such are going to be traveling significantly slower than light speed. The top answer currently links to an article suggesting that current speed measurements of the supernova shockwave are between 8 and 64 miles per second (28,800 or 230,400 miles per hour). Which is basically standing still when compared to lightspeed (clocking in at a whopping 669,600,000 miles per hour). – Lino Frank Ciaralli Jul 19 '16 at 0:50
• Lino, because a large part of the shock are from light (ranging from radio waves to gamma-rays) and neutrinos (which arrive even before than the light because they travel inside the star with negligible interactions). As the top answer notes and already were present elsewhere, "holding a thermonuclear device to your eye would have nine orders of magnitude less radiant energy than a Supernova exploding at the distance of our Sun from you". The only way to escape being vaporized just by the light alone would be to travel outwards at very near the light speed or hiding yourself somewhere. – Victor Stafusa Jul 19 '16 at 1:54